1. Field of the Invention
The present invention relates to an immobilized electrolyte membrane. This immobilized electrolyte membrane can be widely used in, for example, a fuel cell, an electrolytic cell of water, an electrolytic cell of brine, a primary battery, a secondary battery, a membrane for separation of facilitated transport, an electrochromic device, or a sensor, where a low electric resistance and a high mechanical strength of the membrane are required.
2. Description of the Related Art
As a solid polymer electrolyte (SPE), there are known an ion-exchange membrane, typically a membrane of perfluorocarbon-system having a sulfonic group (Nafion.RTM.), an ionic conducting membrane, typically a complex of polyethylene oxide (PEO) and an alkali metal salt such as LiCF.sub.3 SO.sub.3, LiClO.sub.4 and LiAsF.sub.6, and others. Ion-exchange membranes of perfluorosulfonic acid, perfluorocarbonic acid, etc., have excellent chemical and thermal resistances and enable the construction of a compact cell with an anode and a cathode, and therefore have been used in brine electrolysis and are experimentally used in a fuel cell and water electrolysis, and the like. In this connection, a polystylene sulfonic acid type ionic exchange membrane was used in a hydrogen-oxygen fuel cell for space development objectives, but was improved as used for brine electrolysis. More effective perfluorocarbon type ion-exchange membranes have been developed, and most electrolysis processes of chlorine and alkali salts now have been converted to ion-exchange membrane processes. In a system using an SPE problem arises of a reduced electrical energy efficiency due to ohmic loss by an electric resistance of a membrane of the SPE. An SPE membrane using an ionic conductor such as a composite of PEO and an alkali metal salt has an advantage in that it is substantially a solid, but is two to three orders of magnitude lower in the specific electric conductivity than that of an aqueous solution system of a mineral acid, alkali or salt, which limits the use thereof due to the ohmic loss. For example such a polymer electrolyte having a thickness of 50 .mu.m and a specific electric conductivity of 10.sup.-6 S.multidot.cm.sup.-1, has an effective electric resistance of 5000 .OMEGA.cm.sup.2. Reducing the thickness of a membrane may be a solution to the reduction of the electric resistance, but is limited by mechanical strength considerations, and such a membrane of an ionic conductor as having a practical mechanical strength at a thickness of, e.g., not more than 25 .mu.m, is not known. An ion-exchange membrane of perfluorosulfonic acid or perfluorocarbonic acid has an effective electric resistance of 1 .OMEGA..multidot.cm.sup.2 to 100 .OMEGA..multidot.cm.sup.2 or more, and the thickness of this type of membrane is also limited by consideration of the mechanical strength thereof. A membrane of Nafion.RTM., for example, has a thickness of 0.11 mm to 0.25 mm, and a membrane of an ion-exchange resin having a practical mechanical strength at a thickness of not more than 100 .mu.m is not known. Moreover, a fluorine-type ion exchange resin membrane, typically of Nafion.RTM., is expensive.